Configuring the System as a DNS End Resolver

An overview of how to configure the system as a DNS End Resolver.

Summary

This section describes how the system can be configured to provide an end-to-end resolution for DNS queries. It provides instruction for the following tasks:

• Configuring Recursive Resolution on NetScaler
• Removing Recursive Resolution Settings

Configuring Recursive Resolution

A Resolver is a procedure that is invoked by an application program, to translate a domain/host name to its IP address. The resolver interacts with the LDNS, which looks up the domain name to obtain its IP address.

The process of querying different name servers recursively to access the IP address of a domain name is called recursive resolution. Each name server that does not have the IP address queries another name server for the IP address, then reports back.

In recursive resolution, the resolver sends a recursive query to a name server for the IP address of a domain name. If the queried name server is authoritative for that particular domain, it responds with the requested domain name. Otherwise, it queries other name servers recursively until it finds the requested domain name. This process, with an example is illustrated in the following figure.

<<INSERT FIGURE>>

When the name server receives a query for the address of s1.s2.s3.com , it first checks the name servers for s1.s2.s3.com. If the address of s1.s2.s3.com is found in the name server, it responds with a suitable IP address. Otherwise, it queries other name servers for s2.s3.com, then for s3.com, and for com to retrieve the address of s1.s2.s3.com. By default, the querying process for the domain name ends in the root name servers.

It is recommended to enable caching for recursive resolution to function.

Enabling Recursive Resolution

To configure the system to perform recursive resolution, use the parameters listed in the following table.

The following procedure describes the steps to enable recursive resolution.

To enable recursive resolution

1. In the left pane, click DNS. The DNS page appears in the right pane.
2. Click DNS Parameters. The Configure DNS Parameters dialog box appears.
3. Select the Enable recursion check box.
4. Click OK and then click Close.

Setting the Number of Retries

The following procedure describes the steps to specify the number of retries for recursive resolution. By default, the number of retries is set to 5.

To set the number of retries

1. In the left pane, click DNS. The DNS page appears in the right pane.
2. Click DNS Parameters. The Configure DNS Parameters dialog box appears.
3. In the DNS Retries text box, type the DNS resolver request retry count.
4. Click OK and then click Close.

Verifying the Configuration

The following procedure describes the steps to view the recursive resolution configuration.

To view the configuration

1. In the left pane, click DNS. The DNS page appears in the right pane.
2. Click DNS Parameters. The Configure DNS Parameters dialog box appears.
3. The configured DNS parameters appear in this dialog box.
4. Click Close.

Removing Recursive Resolution Settings

The following procedure describes the steps to disable recursive resolution.

To disable recursive resolution

1. In the left pane, click DNS. The DNS page appears in the right pane.
2. Click DNS Parameters. The Configure DNS Parameters dialog box appears.
3. Clear the Enable recursion check box.
4. Click OK and then click Close

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